Telephone-exchange system



Jan. 14, 1930 w|LBUR TELEPHONE EXCHANGE SYSTEM 14 TTORNEV Filed July 6, 1927 Patented Jan. 14, 1930 UNITED STATES PATENT OFFICE RAY S. WILBUR, OF LYNDHURST, NEW JERSEY, ASSIGNOR TO BELL TELEPHONE LAB- ORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK TELEPHONE-EXCHANGE SYSTEM Application filed. July 6, 1927. Serial No. 203,704.

This invention relates to telephone systems and more particularly to improvements in telephone systems employing machine switching apparatus whereby supervisory signals may be transmitted to either a calling subscriber or a calling operator to apprise them of the progress of a connection.

In machine switching systems as now organized, toll calls are usually extended over special trunks extending from the toll switching operators position to a B or cordless operators position and thence over selector switches to subscribers lines. Local calls are terminated over regular incoming and final selectors. In systems employing toll dialing the toll lines terminate at machine switching oflices in special line switches which have access to special district selectors. The toll operator, to establish a toll connection, dials into the sender associated with the special district selector, and the connection is then extended over a toll switching train to the wanted line. Local calls are extended over a train of regular selectors.

It is thus apparent that two separate trains of selectors are employed in an office, one for terminating toll calls and the other for terminating local calls. One of the difficulties which has been encountered and which has necessitated the use of separate switch trains, has been the transmission of supervisory tones, such as busy and ringing tones, and supervisory signals, since tones and signals which are adequate for notifying a local call ing subscriber of the progress of the call are not suitable for similarly notifying a toll operator and for giving the toll operator the necessary answering and disconnect signals. It is therefore the object of the present invention to improve the means for producing and transmitting supervisory signals and tones, and .to associate such meansfwith a selector switch train, whereby the same train of selector switches may be" used for terminating either toll or local connections, thereby materially economizing in switching apparatus and utilizing the switching apparatus'more economically V More specifically the invention, one embodiment of which has been disclosed by way of illustration in the drawing, vprovides means for associating a source of interrupted high frequency tone current which may, for example, be of 1000 cycles frequency interrupted at a rate of 20 cycles per second, with an incoming selector, for the purpose of transmitting to either a toll operator or to a local subscriber a suitable ringing tone when the calling subscriber is being rung, means for associating said source of tone wit-h a final selector for the purpose of transmitting a suitable busy signal if the wanted line being tested is found to be busy, and for transmitting answering and disconnect signals to the toll operator on toll calls when the called subscriber responds or hangs up his receiver.

The drawing shows at the left thereof, a toll operators cord circuit and a local subscribers station both of which have access over line switches to a district selector shown 1n the upper right portion of the drawing, having associated therewith a suitable common sender, saidsel'ector having access to any subscribers line in the exchange over the train of selector switches diagrammatically illustrated in the lower right portion of the drawing.

The toll operators cord circuit 1 may be of well-known type. The line switches diagrammatically shown at 2 and 3, the district selector 4, office selector 46, incoming selector 5, final selector 6, and sender 7 may be of the type disclosed in the patent'to' F. A. Stearn, No. 1,505,171, granted August 19, 1924:, the selectors 5 and 6 being modified, however, as to the tone and supervisory features thereof in accordance with the present invention. Although line switches have been illustrated at2 and 3 it is, of course, obvious that line finders could be used with equal facility and also although the invention has been illustrated in connection with switching appa ratus of the panel power driven type it could be practiced as well with other types of switching apparatus such as, for example, step-by-step switches. Itis believed that the invention will be best understood from a detailed consideration thereof in connection with the attached drawing.

It will be first assumed that the calling subtions in the well-known manner to hunt for and connect with an idle district. selector.

It will be assumed that the district selector 7 4 is idle and that the substation 8 becomes" connected therewith over the line switch 3 I and the trunk conductors 10 and 11. Upon the seizure of the district selector 4, an idle sender 7 becomesassociated therewith in the well-known manner, and a dialing tone is calling subscriber thereupon manipulates the dial 12 to transmit dial impulses to the senderv transmitted to the calling subscriber. The

7 in accordancewith the directory number of the wanted'line 9. These dial impulses are transmitted to the sender 7 over a circuit which maybe traced in part from the substation dial 12 over the tip brush 13'and bank terminal of line switch 3, conductor 10, the lower contacts of sequence-switch spring 14, conductor 15, to the sender 9, thence returning over conductor 16, the left contacts of sequence switch spring 17 conductor 11, the ring brush 18. and bank terminal of switch 3 to the substation dial.

'Following the registration of the wanted line number upon the registers of the sender 7, the sender proceeds to control the setting of the selector switches 4, 46, 5 and 6 in the well-known manner ov'er the fundamental circuit conductors 19 and 20 toextend the connection to the wanted line 9. ]Whenthe final selector 6 has been set upon the terminal's of the wanted line, the sender 7 is dismissed and the talking circuit is established over sprin s 14, 17, 51 and 52 at the district selector I determine if the line is busy. If the line is found to be busy the sequence switch (not shown) associated with the final selector is advanced to the busy signaling position 17 and an interrupted circuit is closed for the control'relay 21, extending from battery through the winding of relay 21, sequence switch spring 22, .to groundthrough the in terrupter 23. Upon each energization of re-' lay 21, a tone circuit is thereupon closed, extending from the secondary winding of tone coil 24, through the secondary winding of tone coil 25, the contact of relay 21, the left contacts of sequence switch spring 26, brush 27'and the bank terminal ofselectorfi, the

lower back contact of relay 28, conductor 29, the winding of supervisory relay 30, the lower right winding of repeating coil 31 to battery. Superimposed on this tone current is e the busy tone current of 60 impulses per minute from the source 47 through the primary of tone coil 25. Tone current is induced into A test is then'made to.

the circuit above traced from the source of high frequency current 32 which may, for

example, have a frequency of 1000 cycles per second, interrupted at a rate of 20 cycles per a second. The tone current in the secondary circuit above traced is induced in the circuit extending from the left-hand windings of repeating coil 31, back over the brushes of the V ofiice selector 46 and of the district selector 4, the upper contacts of sequence switch springs 51 and 52 through the right hand windings of repeating coil 54, and is again induced in the circuit extending through the left windings of repeating coil 54, back to the calling subscribers line. receipt of the busy tone, the callinx subscriber releases the connection in the usual manner If, however, the called line is not busy, the finalselector sequence switch is arrested in the talking position 15 and the ringing of the.

called subscribers bell is initiated at the incoming selector 5 by the energization of the relay 28, in the manner set forth in the'patent to Stearn hereinbefore referred to. Ringing takes place with the sequence switch of the incoming selector first in position 11 and then in position 13. With relay 28 energized and i the sequence switch in position 13, ringing current flows from the rmging current source 33, through the ringing interrupter-34, the 7 terminal of selector 5, to ground at the uppe front contact of relay 28. r 1

During the'application of ringing current,

Upon the a ringing tone is transmitted to the calling subscribers line from the high frequency source 32 which 7 is intermittently changed from high to low volume by the interrupter 41, which is uponthe-same' shaft with the ringing interrupter 32. The interrupter 41 intermittently short circuits the resistance 42 in the ringing tone circuit, thereby changing the volume of the ringing tone. With the short circuit about resistance 42 open, a low 7 volume tone current is transmitted from'the source 32 through resistances 42and 43, the

contacts 44 of relay 28", the winding of relay, I

30, to ground through the lower right winding of repeating coil 31. This tone currentis then transmitted to the calling line in the same manner above described in connection with the busy tone. current. v p

YVhenthe called subscriber responds, relay 36 energizes over the ringing circuit and opens the circuit of rela'y 28 to disconnect the ringing source, and to connectthe talk ing conductors 45 and 29 to the called line. A circuit is now closed for the supervisory relay 30 which may be traced from battery through the lower right winding of repeating coil 31, winding of relay 30, conductor 29, lower back contact of relay 28, brush 27 and bank terminal of selector 5, thence as traced to the called subscribers station, returning over brush 40, the upper back contact of relay 28, conductor 45, to ground through the upper right winding of repeating coil 31. Relay 30, upon energiz'ation, performs the usual supervisory functions set forth in the patent to Stearn above referred to.

It will now be assumed that the toll operator, one of whose cord circuits is shown at 1, desires to complete a toll call to the subscribers line 9. She will therefore insert the plug 48 of her cord 1 into the jack 49 of an idle trunk extending to the machine switching exchange in which the wanted line is located. Upon the insertion of the plug in the trunk jack, the line switch 2 operates in the well-known manner to extend the trunk to an idle district selector 4. As soon as the district selector and an idle sender 7 have been associated with the operators cord circuit, she operates the dial key 50 to associate her dial (not shown) with the cord circuit, and proceeds to dial the wanted subscribers line number. The connection then becomes extended in the manner previously described to the line of the wanted subscriber. Vhen the connection is established to the terminals of the wanted line, the sender 7 is dismissed and the sequence switch springs 14, 17, 51 and 52 establish the talking circuit at the district selector. A circuit is then established for the cord supervisory relay 53, which may be traced from battery through the lower left winding of repeating coil 54, the upper contacts of sequence switch spring 17, brush 55 and bank terminal of line switch 2, the rings of jack 49 and plug 48, lower normal contacts of ringing key 56, winding of relay 53, upper normal contacts of key 56, tips of plug'48 and jack 49, brush 57 and bank terminal of switch 2, the lower left and upper right contacts of sequence switch spring 14, to ground through the upper left winding of repeating coil 54. ,Relay 53 energizes in this circuit and opens the circuit of lamp 58, which became closed at the contact of sleeve relay 59 when the plug 48 was inserted in jack 49. If it be assumed that the wanted line is busy, and that busy tone current from source 32 is induced back upon the established connection through the right windings of repeating coil 54, current is then induced through the winding of the alternating current relay 60, in a circuit extending from battery through the, lower left winding of repeating coil 54, upper contacts of sequence switch spring 17, brush 55 and bank terminal of switch 2, winding of relay 60, condenser 61, brush 57 and bank terminal of switch 2,

lower left and upper right contacts of 'sequence switch spring 14, to ground through the upper left winding of repeating coil 54. Relay 60, which is tuned to respond to current from the high frequency source 32, thereupon intermittently responds under the influence of the busy back interrupter 23 at the final selector 6, and upon each energizati'on closes a shunt about the supervisory relay 53 of the cord circuit, extending from ground through the contact of relay 60, rings of jack 49 and plug 48, thence as traced through the winding of relay 53 to ground at. the upper left winding of repeating coil 54. Supervisory relay 53 thereby intermittently deenergizes, flashing the lamp 58 as a busy signal. Busy tone current from the tone source 47 will also be transmitted over theestablished connection to the calling subscribers line.

Similarly if the wanted line is found to be idle, relay 60 is intermittently operated from the source 32 through the action of interrupter 41 at the incoming selector, to cause the lamp 58 to flash at a different rate, as a signal to the toll operator that the wanted subscriber is being rung. When the wanted subscriber responds, the ringing current source 33 becomes disconnected from the wanted line through the release of relay 28 as previouslydescribed, and the transmission of ringing tone current from source 32 ceases. The extinguishing of lamp 58 is a signal that the wanted subscriber has responded.

When the wanted subscriber hangs up at the termination of the conversation, relay 3O deenergizes and a circuit is established from ground at its back contact, over the contact of sequence switch cam 63, which becomes closed following the termination of ringing, to battery through the winding of relay 62.

With relay 62 energized the source of tone 7 Relay 60 now responds steadily to this induced current from the source 32, and in turn shunts down relay 53 to'close the circuit of lamp 58. The toll operator noting the steady illumination of lamp 38 is apprised of the fact that the called subscriber has restored his receiver, and that she may then proceed to restore the connection.

While the source of high frequency current 32 has been described hereinas of 1000 cycles frequency it is obvious that this source might be of any frequency within the voice range which could be readilyxtransmitted over the talking path extending to the calling subscribers line or to the toll operators position. It is further apparent that this source of signaling current might be employed for tonesthat mightbe desirable for use in super c ting supervisory vising telephone connections' What is claimed is:

1. In a telephone exchange system, a call-' ing line, an operators position, a called line,

a switching train available to either said calling line or to said operators position for extending a connection to said called line, and

means including a source of high frequency current for transmitting supervisory signals to said calling line or to said operators position. V I r 2. In a telephone exchange system, a calling line, an operators position, a called hne,

a switching train available to either said calling line or to said operators position for extending a connection to said called line, and means including a source of current within the voice frequency range for transmitsignals to said calling line or to said operators position. i

3. In a telephone exchange system, a calling line, acalled, line, selector, switches for extendin a connection from said calling line to said called line, and means including a source of current within the voice frequency range for transmitting supervisory tone signals to said, calling line.

4. In a telephone exchange system, a calling line, a called line, selector switches for 1 extending a connection from said calling ,line to said called line, means for. applying ringing current to said called line, and means including a source of high frequency current for transmitting a supervisory tone to said I calling line durin the application of ringing current to sai called line.

5, In a telephone exchange system, a calling line, a called line, selector switches for extending a connection-from said calling, line to said called'line', means for applying ringing current tovsaid called line, a source highfrequency current, and means for transmitting an intermittently varying supervisory tone current from said source to said a calling line duringthe application of ringing current to said called line.

6. Ina telephone exchange system, a calling line, a called line, selector switches for extending a connection fromsaid calling line to said called line, means for applying ringfrequency current, and means including'an interrupter and resistances for transmltting a supervisory tone of intermittently varying VOlume from said source to said calling line during theapplication of ringing current to said called line.

. 7 Q Ina telephone exchange system, an op erators position, a called line, selector 'swltches for extending a connection from said operators posltion to said called line, a

supervisory signal at said operators position,

a relay, means for applyingringin current to said called line, and means inauding a the application of ringing current to said called line. r

, 8. In a telephone exchange system, an operators position, switches for extending a connection from said operators position tosaid called line, a supervisory lamp at said operators position, a relay, means for applying ringing current to said called line, a source ofh1ghfrequency 9. called line, selector current, and means including an interrupter for intermittently transmitting current-from said source to said relayv during the application of ringing current to said called :line

Wherebysaid relay causes said lamp to flash 9. In a telephone exchange system, an operators position, a called line, selector switches for extending a connection from said operators position to said called line, a supervisory lamp atsaid operators position, a relay, means for testing the called line to de termine if it is free or busy, 2. source of high frequency current, and means including an interrupterfor intermittently transmitting current from said source to said relay for causing said lamp to flash if said called line when tested is found to be busy.

10. In a telephone exchange system, a calling line, an operators position, a called line, a switching train available to either said call ing line or to said operators osition for extending a connection to sai called line, a

responsive device on the calling line, a supervisory signal at said operators position, a

relay for controlling said signal, means for applying rmgin current to said called line,

a source of high requency current, and means for applying current from said source to operate either said responsive device or said relayduring the application of ringing cur f 7 rent to said called line.

11; In a telephone exchange system, a call- I ing l ine, an operators position, a called line, a switching train available to either said callsponsive device on the calling line, a super'- relay for controlling said signal, means for .110 a ing l ne or to said operators position for extending a connection to said called line, a reapplying ringing current to said called line,

7 ing current to said called line, a source of high a Source of g frequencylcurrnt and meang for applying current from said source to either producea tone in said'res onsive device or to operate said relay during the ap plication of rin'ging'current to said called line.

12 Ina telephone exchange system, a calling line, an operators position, a called, line, a switching train available to either said calle ing line or to said operators position for extesting said calledline to determine if it is free or busy, a source of high frequency current, and means for applying current from said source to operate either said responsive device or said relay if said called line when tested is found to be busy.

13. In a telephone exchange system, a calling line, an operators position, a called line, a switching train available to either said calling line or to said operators position for extending a connection to said called line, a responsive device on the calling line, a supervisory signal at said operators position, a relay for controlling said signal, means for testing said called line to determine if it is free or busy, a source of high frequency current, and means for applying current from said source to either produce a tone in said responsive device or to operate said relay if iaicl called line when tested is found to be Ir i witness whereof, I hereunto subscribe my name this 29 day of June, A. D. 1927.

RAY S. WILBUR. 

